1. Field of the Invention
The present invention relates generally to the packaging of electronic components. More particularly, the present invention relates to a vertical cavity surface emitting laser (VCSEL) package and method of fabricating the same.
2. Description of the Related Art
Semiconductor lasers, such as vertical cavity surface emitting lasers (VCSELs) are well known. A VCSEL typically included an active area disposed or sandwiched between a first contact, sometimes called a laser anode, and a second contact. During operation, a voltage applied across the electrical contacts generated a current through the VCSEL.
The optical output power of the VCSEL was determined by the amount of current driven through the VCSEL. In certain applications, such as bar-code readers, digital video discs (DVDs) and compact discs (CDs), it was necessary or highly desirable to maintain a fixed optical output power.
The optical output power was maintained at a fixed or constant value through automatic power control (APC). Generally, automatic power control involved directly measuring the optical power output. The measured optical power output was subsequently used to adjust the electrical power input to the VCSEL and, thereby, to maintain the optical power output at a fixed or constant value.
As set forth in Kiely et al., U.S. Pat. No. 6,151,344, APC of a VCSEL was difficult because the VCSEL generally emitted light from only a single surface, thus making direct measurement of the optical power output and subsequent adjustment thereof a difficult task. Conventionally, the task of APC of a VCSEL had been accomplished by manually positioning an optical device or devices such as photodiodes, mirrors, beam splitters, or the like, in the optical path of the emissions from the VCSEL.
Typically, these optical devices were manually positioned with respect to the VCSEL package. However, manually positioning the optical devices presented several problems and disadvantages such as, high manufacturing cost, lack of repeatability, and poor quality control, thus prohibiting high-volume manufacturing.
To avoid these problems and disadvantages, Kiely et al., cited above, taught a semiconductor device, which included a VCSEL and a monolithically integrated lateral photodetector. The lateral photodetector controlled the optical power output of the VCSEL by monitoring or detecting the lateral spontaneous emissions from the VCSEL. The lateral photodetector generated a photocurrent from the spontaneous emissions, which was compared to a reference signal. The difference between the photocurrent and reference signal was used to alter the electrical power input to the VCSEL and thereby to control the optical power output at a fixed or constant value.
However, fabrication of the semiconductor device of Kiely et al. was relatively complex and expensive compared to the fabrication of a standard conventional VCSEL.
In accordance with one embodiment of the present invention, a vertical cavity surface emitting laser (VCSEL) package includes a substrate and a VCSEL device, i.e., an electronic component, coupled to the substrate. The VCSEL device includes a first VCSEL, sometimes called an active area, and a calibration VCSEL, sometimes called an active calibration area. A sensor, e.g., a controller diode, is coupled to the substrate, the sensor including a sensor area aligned with the calibration VCSEL.
The calibration VCSEL is substantially similar to or identical to the first VCSEL. However, light from the calibration VCSEL is measured by the sensor to determine the optical power output of the VCSEL device and, more particularly, of light emitted from the first VCSEL. The measured light is subsequently used to adjust the electrical power input to the VCSEL device to maintain the optical power output of the VCSEL device and, more particularly, of the light emitted from the first VCSEL, at a fixed or constant value.
Also in accordance with one embodiment of the present invention, a method of forming a VCSEL package includes coupling a VCSEL device within a pocket of a substrate. The VCSEL device includes an active area and an active calibration area. Bond wires are formed between bond pads of the VCSEL device and traces coupled to the substrate. A window is coupled to the substrate to seal the pocket. A sensor is coupled to the substrate such that a sensor area of the sensor is aligned with the active calibration area of the VCSEL device.
In one embodiment, the sensor is coupled to the substrate by mounting joints, e.g., solder, sometimes called solder joints. Advantageously, the sensor is mounted with the mounting joints at low cost. Accordingly, the VCSEL package is manufactured at a minimal cost. Further, the sensor is positioned with respect to the VCSEL device with extremely high accuracy as part of the VCSEL package. Accordingly, the characteristics of a plurality of VCSEL packages manufactured in high-volume in accordance with this embodiment of the present invention are highly repeatable.
The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.